Contemporary turbine systems employ a variety of safety systems to monitor and ensure that the system operates in a safe condition. One such turbine safety system is a hydraulic trip valve. Such a valve is situated within the fuel flow to the turbine engine. In the event a safety controller detects on unsafe operating condition of the turbine, e.g. an over-speed condition, the trip valve closes off the flow of fuel to the turbine.
In one such configuration, the trip valve is held open under hydraulic pressure. A trip block is interposed between this hydraulic pressure head and a drain. The trip block includes one or more valves which are held in a closed configuration such that the hydraulic pressure head cannot drain through the trip block to the drain. As a result, the hydraulic pressure maintains the trip valve in an open state.
However, in the event of the above referenced unsafe operating condition, the trip block will be commanded to open, and allow the hydraulic pressure head to pass through the trip block and to the drain. This results in a loss of the hydraulic pressure responsible for holding the trip valve in an open state. The trip valve then closes, and the fuel supply to the turbine is cut off. Contemporary trip blocks typically include multiple redundant valves, such that if one valve does not open, the others will, and the aforementioned draining function will still occur.
While such systems have proven to be effective, the trip block is not without its deficiencies. For example, one typical embodiment of a trip block is a plurality of stand-alone valves which are interconnected to one another via exterior plumbing. In the event one valve fails, the others will still move to open and allow the aforementioned draining function to occur. This embodiment tends to require a large footprint of space, and due to its exterior plumbing, has multiple failure points and is relatively complex.
Another typical embodiment of a trip block is a plurality of valves which are connected to a manifold. Each valve has its own stand-alone housing. The manifold is typically a separate housing with a plurality of passageways. The valves are mounted at various locations on the exterior of the manifold housing by mounting the valve housing of each valve to the manifold housing. This also results in a large footprint design. Further, given that each valve has its own housing, and the manifold itself is a relatively large housing, the overall weight of such an embodiment is also not desirable.
Further, in both of the above described embodiments, certain implementations thereof do not allow for the usage of the trip block when a replacement of one of the failed valves thereof is occurring. In other words, the entire system, including the turbine, must be taken off line to repair the trip block.
Yet further, contemporary trip blocks typically employ valves which require high actuation forces, and as such, high powered actuators. Such actuators increase the cost of operation of the system, and also add to its size and weight. Indeed, contemporary trip blocks typically employ linearly moving valve elements. These linear elements require tight radial clearances to keep the linear element centered to reduce leakage. These tight clearances can become jammed with contamination if the hydraulic fluid is not filtered to appropriate levels, typically ISO 4406 class 16/13 or cleaner.
In view of the foregoing, there is a need in the art for a compact, lightweight, trip block which requires a relatively small actuator for each of the valves employed thereby.
The invention provides such a trip block. These and other advantages of the invention, as well as additional inventive features, will be apparent from the description of the invention provided herein.